The present invention relates generally to processes for controlling environmental pollution, and more specifically, to chemical means for decontaminating substrates polluted with toxic substances.
The great difficulty in controlling toxic environmental pollutants is implied in the shear tonnage of the chemical industries production. Whereas 25 million gallons of benzene solvent were manufactured in 1940, by the 1980's, this figure exceeded 2 billion gallons per year in the United States alone. In the last twenty years the production of general organic solvents rose more than 900%, while during the same period the production of plastics increased by more than 2000%, and synthetic fibers, for example, more than doubled that figure.
Unfortunately, however, the technology for handling and disposing of toxic waste and chemical by-products has not kept pace with the enormous growth of industry and its requirements for chemicals. In response to this problem, a new industry, the hazardous waste disposal industry, developed. The new industry promised to neutralize or recycle wastes but no innovative technology to meet the growing problem economically developed. As a result, waste handlers have been forced to resort to land disposal, which is a storage technology and not a disposal technology, and only postpones the problem of ultimate disposal. In some instances, the toxic chemicals have been carelessly discharged into the environment, e.g. onto grounds or into landfills having inappropriate subsoils, and the like. For example, waste oils contaminated with dioxin, transformer oils containing polychlorinated biphenyls (PCB's), and a wide variety of waste solvents have been discharged, causing contamination of water supplies and creating other potential health risks.
Attempts to respond to leaking tank cars, spills and other environmental events and to decontaminate polluted grounds and other surfaces exposed to toxic substances frequently are met with delays and/or inadequate corrective measures. Often, time is of the essence to minimize environmental impact. Yet, cleanup can mean a relatively slow and costly process, e.g. removing the polluted substrates, such as by reclamation where, for instance, contaminated earth is excavated and transferred to a different location. Other methods of treating envorinmental events are either unreliable or not adequately spontaneous as to be amenable to on-site treatment of the exposed substrate. Accordingly, one aspect of the present invention provides for a more spontaneous process of decontaminating substrates which have become polluted with toxic substances by treating the subsrate at the situs of the event thereby reducing the potential for damage to the environment.
Numerous agricultural chemicals have recently been found to be potentially toxic or environmentally harmful. Agents such as pesticides, herbicides, fungicides, and fertilizers which are applied to large areas of ground in tonnage quantities are now being examined and in some cases banned for future use because of their toxicity. Materials such as DDT, chlordane, and chlordecone are now severely restricted. In high concentrations these materials pose a serious health threat as they leach into the aquifiers. Inexpensive, efficacious means for removing these materials from the soil or for destroying them in-situ do not presently exist. A further aspect of the present invention relates to an improved method for treating tonnage quantities of soil inexpensively with materials which are environmentally benign.
Halogenated compounds have a wide variety of practical applications, e.g. agriculture, horticulture, soil fumigants, solvents, to name but a few. Many of these materials are toxic to plant and animal life. Although some halogenated materials are photo-and/or biodegradable and eventually disappear from the environment, a substantial number and particularly the polyhalogenated organic compounds are stable and resistant to degradation. The presence of these materials in otherwise useful materials creates a double disposal problem, for not only must the toxin be disposed of, but also the material it contaminates, greatly increasing the overall volume of material requiring disposal. For instance, PCB's, once commonly used as transformer dielectric fluids, are a persistent source of contamination in replacement dielectric fluids. Several methods are presently being used for treating such contaminated chemically inert liquids. One such process generally referred to as the alkali metal or active metal process relies on heterogeneous reactions between solid sodium metal and halogenated organic materials in solution with mineral oil or other inert liquid. Processes of this type are hazardous because alkali metal can react violently with the halogenated contaminant. Furthermore, the process of destroying the toxic material is quite slow-because the heterogeneous reactions taking place require mass transfer of a solid phase material through the contaminated liquid phase. Accordingly, the present invention also contemplates an improved process for decontaminating/recycling chemically inert liquids, by a substantially spontaneous homogeneous reaction which destroys the toxic substance with a product of alkali metal while avoiding the direct use of such reactive metals per se as reducing agents in the process.